The terms of Article 50 of the Lisbon Treaty, the legal mechanism for quitting the EU, states a country deciding to quit the bloc “shall notify the European Council of its intention”.

It is reported the Prime Minister is hoping to formally tell European Council president Donald Tusk of Britain’s desire to exit the EU on March 9, ahead of a two-day summit in Brussels.

Mr May this week hailed how she had “moved a step closer” to meeting her notification deadline following MPs’ overwhelming backing for the Government’s Article 50 Bill on Wednesday night.

If now passed by the House of Lords, the Prime Minister will have full authorisation to trigger the two-year timetable for divorce talks.

But what should Mrs May be including as she drafts her Article 50 notification? And does it need to be a formal letter?

SCOTLAND, NORTHERN IRELAND & WALES

Michael Russell, the Scottish Government’s minister for Brexit negotiations, this week demanded the Prime Minister include Nicola Sturgeon’s demand for a “differentiated” Brexit for Scotland to the rest of the UK within her Article 50 notification.

The SNP minister also claimed the Scottish Government didn’t believe Article 50 notification could be sent until Mrs May has agreed with Scotland, Wales and Northern Ireland the form of the letter to launch divorce talks.

Mr Russell told a committee of MPs: "We don't believe that triggering Article 50 can be done unless … there has been an attempt to get an agreement on the letter."

DOES IT REALLY MATTER?

Despite demands from politicians, lawyers from both sides of the Brexit debate have insisted the form of the Prime Minister’s notification is of little significance, other than it actually being delivered.

Martin Howe QC, chairman of the pro-Leave Lawyers for Britain group, told Express.co.uk: “It can be a very short formal document. There is no purpose in putting negotiating aims etc. into this formal document although they could be put forward at the same time but separately.”

The leading barrister pointed to Britain’s notification of withdrawal from the European Free Trade Association (EFTA) in 1972 (see below) as an example for Mrs May to follow.

The letter was recently produced in the Supreme Court hearing into whether the Prime Minister needed Parliament’s consent prior to invoking Article 50.

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The letter of notification when Britain quit EFTA in 1972

Jolyon Maugham, a fellow QC, described debate about what Article 50 notification should include as a “red herring” and suggested there was no “formal mechanic” for notification.

The Remain supporter said: “I think what Article 50 envisages is a notification that we are leaving and there's no requirement for that notification to be on bonded letterhead paper.

“It is enormously significant in that it starts the two-year clock running but it has no function other than to start that clock running.”

Mr Maugham said there was “chatter” about whether or not Britain might deliver a conditional or reversible notification of EU departure, but added: “I rather doubt such a thing is possible and I'm quite certain that such a thing is not intended by the Government.”

He said: “There is no need or requirement or, certainly as far as I’m concerned, expectation the notification will be anything other than ‘we notify you we want to leave the EU’.”

It's finally here.

Continued cooperation with the EU to tackle terrorism and international crime.

AN EXAMPLE

Helpfully for the Prime Minister, leading eurosceptic and Tory MP John Redwood has already drafted an Article 50 letter for her to use. As published on his website, it states:

Dear Sirs

The UK as a result of a referendum has decided to withdraw from the European Union. In accordance with Article 50 we hereby notify the Council of our intention to leave.

Article 50 of the Treaty states clearly that “any member state may decide to withdraw from the Union in accordance with its own constitutional requirements.” In the case of the UK this means passing an Act of Parliament. The UK government has always confirmed when asked about the loss of sovereignty involved in EU membership that the UK Parliament remains sovereign because it can repeal the 1972 European Communities Act. The government is introducing a Bill to effect this change, and to transfer all EU law into UK law to provide immediate continuity.

The UK wishes to continue with strong trading, investment, business and other links with our friends and former partners on the continent. The UK is not proposing any new barriers to our mutual trade, and will be happy to continue with all the business and trade arrangements and business rules currently in place. These will be confirmed in UK law as we make the necessary constitutional changes. If the rest of the current EU does wish to consider placing new tariffs and barriers on our mutual trade, then we will be willing to come to talks to discuss how these might work. They would of course need to be compatible with World Trade Organisation Rules, and with Article 8 of the Lisbon Treaty which states that “The Union shall develop a special relationship with neighbouring countries, aiming to establish an area of prosperity and good neighbourliness.”

The UK has voted to withdraw from the Treaty and is doing so in accordance with Article 50. It also does so under the Vienna Convention on the law of Treaties by invoking a “fundamental change of circumstances” compared to those when the UK consented to the Treaty.